Synchronizing mechanism



Patented Nov. 5, 1940 UNITED STATES PATENT OFFlCE (Granted under the act of March 3, 1883, as

I amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

It is an'object of our invention to synchronize a plurality of prime movers which during normal operation may vary in revolutions per unit of time from one another or from a master speed oi rotation device.

More specifically, our invention relates to appak ratus for synchronizing a plurality of such prime movers as those encountered in multi-engined aircraft power plants in order to reduce to a minimum structural vibrations and'auditory fatigue caused by the operation of the engines of suchpower plants out of synchronism.

It is well known to those skilled in the art that aircraft employing multiengined power plants having more than one propeller, are subject to a very disagreeable beat or drumming noise whenever one or more engines rise'above or fall below the operating revolutions of the power plant as a whole. The aforesaid phenomena subjects the personnel operating the aircraft to severe auditory fatigue and may set up destructivevibrations in the aircraft structure itself.

In aircraft employing only two propellersit is a comparatively simple matter to eliminate beat phenomena due to engine revolution inequalities by merely varying the speed of revolution of one of the aforesaid engines until they "beat disappears. However, when three of more propellers are employed, it will be readily seen that elimination'of the beat phenomena becomes a highly complicated matter because of the fact that it is extremely 'diffic'ult for operating personnel of the aircraft to tell which propellers are causing the beat. Previously, therefore, this difficulty has proven a serious drawback to the extended-use of airplanes having three or more independently driven propellers, particularly for use in carrying passengers. The safety feature introduced by the greater number of independently driven propellers, however, is'extremely desirab1e.

It is of course possible to set engine revolutions approximately the same by using the tachometers attached to each engine. but it is impossible with tachometers alone'to set engine revolutions close enough to a master revolution indicator to eliminate the objectionable "beat referred to above.

It is therefore a second object of our invention to provide a synchronism indicator, where it is not desired to use automatic synchronism control, in

order that engine revolution variations may be corrected manually,

It is a still further object of our invention to automaticallysynchronize the engine revolutions of multi-engined aircraft power plants.

Other objects and advantages of our invention will become apparent from the following description taken in connection with the accompanying drawings, it being clearly understood that the same are byway of illustration and example only and are not to be taken as in any way limiting the spirit or scope of our invention. The spirit and scope of our invention is to be limited only by the terms of the appended claims.

Referring to the drawings, in which numerals of like character designate similar parts throughout the several claims:

Figure 1 is a diagrammatic view of one embodiment of our invention;

Figure 2 is a partial cross-sectional view taken on the lines 2--2 of Figure 3;'

Figure 3 is a partial cross-sectional view taken on the lines 3-3 of Figure 2;

Figure 4 is a cross-sectional view taken on the line 4-4 of Figure 2;

Figure 5' is a fragmental view of a second embodiment of our invention; and

Figure 6 is a fragmental View of a third embediment of our invention.

In Figure 1 lead wires l and 2, from a direct current source not shown, are operably connected with a direct current motor constituting a master speed device 3 and a rheostat 4. One extremity of the master speed device 3 is provided with I a tachometer 5, while the other extremity thereof is providedwith a drive shaft 6, surmounted by a worm gear 1. The worm gear I is operablyengaged with another worm gear 8, mounted on a driven shaft 9 of. a synchronizing mechanism in. The internal elements comprising the synchronizing mechanism ID will be described in detail in connection with Figure 2. For the present, external wiring and parts associatedtherewith need only be described. A lead wire II is connected to one pole of a constant current source [2. Passing from left to right, lead wires l3 and I4 are operably associated with the first engine'of a multl-engined power plant through connection with a reversible motor 29a, while three additional pairs of lead wires I5 and I8, then I! and I8, then I9 and 20, are operably associated with a second, then a third, then a fourth aircraft engine, through connection, re-

spectively, with reversible motors 2912.190, and 29d. Between terminal ends, the lead wire I3 is provided with a light 2 l, as are successive lead wires l4, l5, I6, [1, l8, l9 and 20 provided, re-

- of the aircraft, upon 28. The remaining pole of the constant current source I2 is brought into common electrical connection with theremaining third lead wires of the reversible motors 29a, 29b, 29c and 2911 by means of a wire 30.

' As will be more specifically apparent after description of Figure 2, it is a dual object of our invention to provide for both manual and automatic operation. of the synchronizing mechanism l8. For both systems of control, we therefore further provide throttles. 3la, 31b, 31c, and 3ld, which are operably connected respectively with the first, second, third and fourth engine of the aforesaid multi-engined power plant. The synchronizing mechanism If! is also provided with four additional pairs of lead wires 32 and 33, then 34 and '35, then 36 and 31, and then 38' and 39. The lead wire 32 is operably connectedwith one pole. of an interruptor unit 40a forming a part of and driven by the aforemen ioned first engine. The other pole of the unit 40a is connected with one pole of a'constant current source Ma. The remaining pole of the current source 4! a is operably connected with lead wire 33. From the diagrammatic showing of Figure 1, it is at once apparent that the remaining three pairs of lead wires are similarly interconnected with the remaining three pairs of interruptor units and current sources.

The throttles 3la through 3111 are provided with mounting shafts 42 fixed to the structure which are mounted levers 43, surmounted by handles 44. The levers 43 are provided with push rods 45, secured by cotter pins 46. They are further provided with worm gears 41, against which frictionally engaged driving plates 48, fixed to the base portions of the lever 43 by rivets or other suitable attaching means. The reversible motors 29a through 29d are provided with drive shafts 49 and worm gears 50 adapted to operably engage the worm gears 41 discussed above. We have thus provided for both automatic and manual adjustment of the throttles 3la through 3Id, the details of which will be more readily apparent after description of the internal parts of the synchronizing mechanism I0.

In Figure 2, end portions of the drive. shaft 6 and the worm gear l of Figure 1 are shown in operable engagement with the worm gear 8. It will be noted that the latter gear is fixed to the driven shaft 9 of Figure 1 by means of a pin 5!. The driven shaft 9 is supported by means of a U-shaped member 52. Within the limits of the U-shaped member 52,- the outer portions of the driven shaft 9 are provided with master disks 53a and 53b, fixed against lateral or rotational movement by means of pins 54. The periphery of the master disk 53:: is provided with a conductor ring 55. A conductor bar 56, parallel to the driven shaft 9, is fixed to the insulated portions of the master disks 53a and 53b by means of a conductor pin 51. Electric current from the lead wire ll, of Figure 1, is supplied to the conductor bar 56 by means of a conductor brush 58 hearing against the lowermost portion of the conductor ring 55. To prevent side play of the above described disk assembly, the driven shaft 9 is provided with washers 59, separating the outer disk faces from the inner end surfaces of the U- shaped member 52.

Four pairs of auxiliary disk units 62a, 52b, 62c and 62d are longitudinally yieldingly interposed between the inner surfaces of the master disks 53a and 53b by means of springs 60 and washers spectively, with lights 22, 23, 24, 25, 26, 21 and' 6!. The inner auxiliary disk units 62b and 620 are fixedly spaced from each other by means of a washer 63, the same fixed spacing being maintained between auxiliary disk units 62a and 6211, then 620 and 52d by means of further washers 63. Each of the aforesaid units have in common left hand disk 64, right hand disk 65, both of which are provided with like sector openings 66, conductor rings 61, four roller pins 68; four rollers 69 and a central rachet wheel 10. The rachet wheel 10, while free to turn about the rollers 69 even when the disks 64 and 65 are held stationary or vice versa, still acts as a frictional -driving medium to change angular relationship between each auxiliary disk unit and the fixed master disks 53a and 53b due to the presence of the springs 60 and washers 6|. The aforesaid angular change is limited, however, to but a small percentage of the sector opening 66. From left to right the four pairs of conductor rings 61 are maintained in electrical connection with lead wires l3 and 14, then l5 and I6, then [1 and I8, then l9 and 20, by means of eight conductor brushes 58.

Figures 3 and 4 bring out the manner in which the conductor bar 56 is brought intov electrical connection with two or more of the conductor brushes 58.

Reference to Figures 2 and 4 indicates that the far side of the conductor bar 55, as viewed in Figure 2, is provided with four equi-spaced contact points 1|, while the near side thereof is provided with four similarly equi-spaced but not oppositely disposed contact points 12. The contact points 1! are adapted to be rotated in a clockwise direction (Figure 4) into operable engagement with. four oppositely disposed contact points 13, fixed to the outermost surface of four supporting springs 15. In like manner the 'four contact points 12 are adapted to swingin a counter-clockwise direction into operable engagement with four oppositely disposed contact points 14, fixed to the outermost surface of four additional supporting springs 15. Recesses 16 are provided in the four' left hand disks 84, as indicated in Figure 4. The

recess arrangement of right hand disks 85 is just opposite to that of the showing of Figure 4; i. e.,

each of the inner disks 6% and 65 are provided with but one supporting spring 15, the opposite face of the sector-like opening .66 being plain. Each of the springs 15 are secured to its immediatesupporting disk by means of a screw 11 and is electrically connected to its encircling conductor ring 61 by means of a connector wire 18, soldered at its outer extremity 19.

Referring to Figure 3, the synchronizing mech anism I0 is provided with four impulse motors 80. Each impulse motor 80 consists of a mounting frame 8!, a magnetic coil 82, and a magnet bar 83. Themagnet bar 83 is secured to the mountingframe 8! by means of a hinge 84. A rachet pawl 85 is hingedly secured to the lower extremity of the magnet bar 83 by means of a hinge 86. It will be noted that lead wires 34 and 35 protrude from the rear extremity of the imall) pawl-spring 88 is secured to the mounting plates 81a and 81b by means of a pin 89. Outward movement of the magnet bar 83 is limited by a pin 90, while inward movement of the engaging tip of the rachet pawl 85 is limited by means of a second pin 9|. Each inward impulse of the magnet bar 83 will rotate the rachet wheel I one tooth distance. In order that return of the rachet pawl 85 not return the rachet wheel I0 to its original position, a second rachet'pawl 92 is provided. The rachet pawl 92 is secured to the mounting plates 81a and 81b by means 'of a pin 93, the rachet pawl being held in operable engagement with the teeth of the rachetwheel I0 by means of a pawl spring 94 fixed to the mounting plates 81a and 81b by means of a nonrotatable spring support 95. The foregoing concludes description of all those elements essential to the operation of the first embodiment of our invention.

As has been previously stated, operation of the first embodiment of our invention is twofold.'

Referring to Figure 1, let it be momentarily assumed that the reversible motors 29a, 29b, 29c, and 29d are removed, that the wire 30 is directly connected with lead wires I3 through 20, and that the master speed device 3 has been brought up to and held constantly at X clockwise revolution per minute, as viewed in Figures 3 through 6. Under the aforesaid conditions, the rachet wheelsl0 (or I04 of Figure 6) of the four auxiliary disk units 62a through 62d will remain stationary with respect to the impulse motors 80 .(or worm gears I05 of Figure 6) while the remaining auxiliary disk, unit parts, driven by continuing contact between contact points II and I3, will rotate at the same speed as the driven shaft 9. As long as all of the aforesaid auxiliary disk units are driven through continuing contact between contact points, the electric circuits defined by lead wires II and |330, II and |530, II

plant, upon which are respectively mounted the interrupter units 40a through 40d, are'successively started, brought up to, and held constantly at Y revolutions per minute; at whichvrevolution rate the impulse motors 80 (or' worm gears I05 of Figure 6) are designed to effect like revolutions of'the rachet wheels I0 (or I04 of Figure '6) and the auxiliary disk units 62a through 52d supporting the same. Under the aforesaid conditions, the lamps 2|, 23, 25 and 21, will still remain illuminated. However, if one or more of the aforesaid engines is momentarily speeded up," then dropped back to Y. revolutions per minute, through very slight manual advancement, then immediate retardation, of the appropriate throttles 3Ia, 3|b, 3|c or 3Id; one or more of the lights 2|, 23, 25 or 21, will discontinue burning. The aforesaid momentary speeding up results in freeing of the appropriate contact points 1| and 13, through clockwise advancement of the appropriate auxiliary disk unit 52a, 82b, 620 or 62d. It is probable'that one or more of the associated lamps 22, 24, 26 or 28 will become illuminated, in which case it will be necessary for the aircraft pilot to infinitely slightly retard,

then return, the appropriate throttle 3Ia, 3|b,

'3Ic or 3Id to its initial setting to cause the conductor bar 56 and its oppositely staggered contactpoints II and I2' to seek a position substantially midway between the oppositely staggered contact points 13 and I4 installed upon oppositely staggered faces of the sector-like openings 06, the.auxiliary disk units 62a through 6211/ As has been stated before, the second set of lamps may also be differently colored from their predecessors to aid the pilot in more readily distinguishing between "advancement and retardation of any one or more specific engine revolutions per minute with respect to the master speed device -3. We have thus set forth operation of the manual adjustment of our synchronizing mechanism I0.

Automatic operation of the first embodiment of our invention is accomplished as follows. Referring to the actual parts disposition of Figure l, lighting of the lamps 2|, 23, 25 and 21 closes the electrical circuits represented by the lead wire II, the constant current source I2, the wire 30and reversible motor lead wires I3, I5, I1 and I9; causing clockwise rotation of thedrive shafts '49 and worm gears 50, as viewed from right to left, thereby inducing further clockwise rotation of the associated worm gears 41 and levers 49. Throttle advancement continues until the first, then second, then third, and then fourth engine of the heretofore mentioned multi-engined power plant are brought up to the aforementioned Y revolutions per minute; at which point further advancement is automatically,stoppe d by the impulse motors 80 (or the worm gears I05 of Figure 6) slightly exceedinglike revolutions 'of the rachet wheels I0 (or I04 ofFigure 6),

28. We have thus completely described operation of the automatic adjustment of the first embodiment of our invention.

As has been previously stated, many and varying forms of sub-assembly units may be employed to effect both manual and automatic adjustment of our synchronizing mechanism ID. A second embodiment of driving means for the rachet wheels" is shown in Figure 5, The impulse m0- tor 80 of Figure 3 is replaced by a fiuid impulse motor 99. The impulse-motor 90 is composed of a Sylphon 91, provided at its inner extremity with a rachet pawl 98, secured by means of a pawl hinge 99. In order that positive engagement between the pawl 98 and tooth surface of the-rachet wheel I0 may be assured, the forward extremity of the Sylphon 91 is also provided with a pawlspring I00, fixed by means of a rivet I0| or other suitable attaching means. The mounting plate arrangement of Figure-3 is retained in Figure 5,

as are the limiting pin 9|, rachet pawl 92, pawl hinge 93, pawl spring'94 and the spring support 95. A base I02, of the Sylphon 91,,is provided with a fluid pipe. It is at once obvious that the contactor units 10a I through 40d and current sources a. through Md, of Figure 1, will be replaced by any one of severalwell known embodiments of fluid impulse motors; secured directly to and ,driven by the first, then second, then third, then fourth engines of the heretofore mentioned multi-engined power plant. Figure 5 primarily involves the internal mechanism of the synchronizing mechanism Ill, that is, all of the other operating parts of Figure 1, excepting contactor unitsand current sources, remain unaltered in their operation both in the manual and automatic adjustment of the second embodiment of our invention.

Figure 6 shows a third embodiment of our in-. vention, in so far as the synchronizing mechanism In is concerned. The fluid impulse motor 96 and the rachet wheel. 10 of Figure 5-are replaced by a rachet wheel I04 and a worm gear 105 driven by a conventional tachometer drive shaft I06 in direct communication with the first, then second, then third, and then fourth engine of the heretofore mentioned multi-engined power plant. If desired, one of the aforesaid engines may be substituted for the master speed device 3,.of Figure 1, by simply connecting an independent tachometer drive shaft therefrom to the worm fit gear I. As was the case in the second embodiment of our invention, the third embodiment thereof primarily involves internal modification of the synchronizing mechanism l0, and the manual or automatic adjustment thereof is effected in the manner indicated in Figure 1, excepting omission of the contactor units and current sources shown therein, which are replaced by the tachometer shafts I06.

Although the description is specific to the illus means driven by said reference speed-means about an axis coaxial with each of said prime mover driven means, all of said driven means rotating in the same direction, and means operatively responsive to a difference in the speeds of said reference speed driven means and said prime mover driven means, respectively, for actuating a corresponding regulating means to thereby obtain a predetermined speed relation between each prime mover and said referencespeed means. a0 2. In an apparatus for synchronizing a plurality of prime movers, individual means for regulating said prime movers, a variable reference speed means, a plurality of prime mover driven means, rotatable means driven by said reference speed means about an axis coaxial with each of said prime mover driven means, and electrical means operatively responsive to a difference in. the speeds of said reference speed driven means and said prime mover driven means, respectively,

.for actuating a corresponding regulating means to thereby obtain a predetermined speed relation between each prime mover and said reference speed means.

3. Means for obtaining a constant speed relation between aplurality of prime movers and a constant speed reference means comprising, in combination, a plurality of engine driven means, a single means driven by said constant speed means associated with said engine driven means, and a plurality of electrical servo-motor means individually operatively responsive to differences in the speeds of said reference driven means and said engine driven means, respectively, for regulating said prime movers whereby constant speed relations therebetween are obtained.

4. A device for controlling the speeds of a plurality of prime movers comprising, in combination, a support, a reference speed driven member carried by said support, a corresponding plurality of prime mover driven members freely rotatably mounted on said driven member, individual means 'carried by said support and adapted to actuate said freelyrotatable members, and make and break means interposed bet-ween said reference speed driven member and saidplurality of freely rotatable members, respectively, to make or break contact with changes in the speed relation between said reference speed means and any freely rotatably mounted on said first mentioned member, a corresponding plurality of means carried by said support for respectively rotating said freely rotatable members in the same direction has-that of said first mentioned member, a corresponding plurality of pairs of oppositely facing contact points carried by said first mentioned members, each of said freely rotatable members having a pairwof spaced contact points, one positioned for engagement with one and the other positioned for engagement with the other of an associated pair of oppositely facing contact points to make or break contact with changes in the speed between said first mentioned member and said individual freely rotatable member.

cam. J. CRANE. GEORGE a. 1.1mm. 

